BOSTON, DEC. 12 -- Amtrak's "Night Owl" train from Washington to Boston jumped the track while approaching Back Bay Station today and plowed into the rear of a stopped commuter train, creating an underground inferno of fire, smoke and twisted steel that sent more than 250 passengers and rescue workers to several hospitals.

It was a miracle that no lives were lost during the morning rush-hour crash, according to state and local officials, who said about 190 passengers were aboard the 10-car Night Owl and about 900 on the eight-car commuter train operated by Amtrak for the Massachusetts Bay Transportation Authority (MBTA).

"The visibility was about zero," Fire Lt. Michael Walsh said, describing the scene as he entered the burning tunnel. "There was cement, steel and locomotives just incredibly smashed."

Stunned passengers recounted a rail-commuter's nightmare -- darkness, screams, thick smoke and people trapped in twisted metal. Walsh, face blackened with soot, said he saw no panic and even cited "an eerie calm."

Authorities had no immediate explanation about why the Night Owl derailed or about its speed as it left the tracks about 500 feet short of the station platform. Few of the Night Owl passengers were from Washington. As many as 100 were commuters, who boarded at an unscheduled stop in Attleboro, Mass., and most of the rest had boarded in New York; New Haven, Conn., or Providence, R.I.

The Night Owl, which has 22 sleeper berths, was being operated by Richard Abramson, 41, an apprentice in his first week at the controls of a passenger train. He was guiding the train toward its next-to-last stop after the overnight run from Washington.

Amtrak officials said it was "routine" for Abramson to be at the controls and stressed that he was being supervised by an experienced senior engineer, Willis Copeland, 53. Abramson had undergone four years of training and was fully qualified on operating rules and physical characteristics of the route, Amtrak spokeswoman Sue Martin said.

Abramson was among the few people severely injured when the first of the Night Owl's two locomotives rammed the locomotive at the rear of the commuter train, mangling the massive machines and spilling and igniting about 1,500 gallons of diesel fuel. He suffered a broken back and collarbone and facial injuries, authorities said.

Investigators from the National Transportation Safety Board arrived here this afternoon and began coordinating federal, state and local inquiries. Of prime interest, officials said, is the "train tape," an automatic recording device that notes speed and response to signals.

Susan Coughlin, vice chairman of the board, told reporters tonight after viewing the crash scene that she had no findings or conclusions to offer. She said that the tapes had been removed from both trains and sent to Washington for analysis and that all crew members and dispatchers were being tested for signs of drug or alcohol use.

Thomas Glynn, general manager of the MBTA, the state agency that runs mass transit in Greater Boston, said it was "premature" to speculate about the cause.

Glynn said that, after the Night Owl derailed, it sheared off seven or eight vertical beams supporting the tunnel roof, then slammed into the rear of the commuter train, which was making a scheduled stop.

Several officials speculated that the configuration of the two trains helped to minimize injuries.

The Night Owl's two locomotives were pulling two baggage cars, two passenger coaches, a cafe car, a sleeper car and two more baggage cars. The commuter train, which originated in suburban Stoughton, had seven passenger cars pushed by a locomotive. Its engineer ran the train from a cab in the front car.

Deputy Fire Chief Kevin J. Mochen, among the first of many rescue workers at the scene, said he initially saw "hazy smoke, smoke pouring from the vents and emergency exits. Amazingly, there was no panic."

At the point of impact, he said, diesel fuel ignited when it touched hot engine parts. The resulting fire filled the rail tunnel with acrid smoke, and it burned paint and identifying marks from the locomotives.

"The two locomotives and baggage cars took the brunt," Mochen said. "That's why we didn't have loss of life." He added that the engines struck with such force that he could not tell what they were when he arrived. Amtrak officials said each of the Amtrak locomotives weighs about 125 tons.

Walsh said that firefighters shared breathing masks with passengers and that many of his crews worked without masks. Copeland and Abramson had to be extricated with the metal-crunching "jaws of life" tool, he said.

Fire Lt. Jack Joyce brought breathing equipment for the Amtrak engineers and waited with them for more help to arrive while other firefighters kept flames at bay outside, the Associated Press reported. "They were totally dazed and completely out of it," Joyce said.

He said the trains were so mangled that he had no idea in which part of the train the engineers were trapped. "All we were doing was crawling into holes," he said.

Spokesmen at Massachusetts General Hospital, which treated at least 97 people, and the New England Medical Center, which took 36 passengers, said none of their patients was from the Washington area. At street level, fire engines, ambulances and other rescue vehicles clogged streets around Copley Place, a shopping mall that began filling with shoppers soon after the crash about 8:30 a.m. City buses were pressed into service to help commuters around the closed station.

Back Bay Station serves the Boston subway system, the MBTA commuter rail and Amtrak intercity service. Operations resumed on the subway's Orange Line soon after the crash because its cars run on tracks separated from the crash site by a concrete wall. Its tracks are among nine sets of tracks in the station area.

Engineer Copeland, who joined Amtrak in 1983 after a long career at Conrail, was involved in a crash the next year between two Amtrak trains that killed one passenger. He was engineer of a southbound train that collided with one northbound on the same track in a residential neighborhood of Queens in New York.

The safety board and Federal Railroad Administration concluded that the accident was caused by human error, but the agencies cleared Copeland, an Amtrak spokesman said last night.

In November 1987, at Back Bay Station, more than 100 people were injured in the crash of two MBTA commuter trains operated by Amtrak. One train struck the other from behind on the same track, and a faulty signal was blamed.

The safety board called for a federal rule requiring installation of a system that would automatically separate trains. That rule has not been adopted. Since then, the station has been rebuilt, along with the tracks that run between it and South Station. Its tracks are among the newest tracks in the Amtrak system, and the signal system is new.

Staff writer Stephen C. Fehr in Washington contributed to this report.